Mulberry Tree

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The black mulberry originates in Central Asia and is now often grown in gardens for its delicious fruit. Old trees can have very gnarled bark and branches that droop to the ground, where they may take root. Photo by The Board of Trustees of the Royal Botanic Gardens, Kew


Morus nigra and Morus alba

There are about twelve species of mulberries, all of which are deciduous flowering trees in the family Moraceae. This large family also includes tropical trees such as the breadfruit (Artocarpus altilis) as well as the edible fig (Ficus carica) and its numerous relatives. Many of the mulberries grow in tropical regions of Africa and the temperate parts of Asia and North America, but two important species commonly grown in gardens today are the black mulberry, Morus nigra, which originates in Central Asia, and the white mulberry, Morus alba, from China, where it has been cultivated as an essential part of the silk industry (sericulture) for over four thousand years.

The white mulberry is a fast-growing, small to medium-sized tree with a sprawling crown and a rugged trunk. Its leaves can vary markedly in size and shape, from smooth to deeply lobed on one side only or both. The male and female flowers are usually found on separate trees, and the male catkins have one surprising accomplishment—they are noted for their rapid release of pollen. The stamens act like a catapult and fling pollen at approximately 560 kilometers (350 miles) per hour—over half the speed of sound, making it the fastest known movement yet observed in the plant kingdom. The fruits are like blackberries in shape and change in color from white when young to burgundy-red or purple when ripe. They are said to be toxic when immature and when ripe are bland in taste compared to the black mulberry.

The white and the black mulberry, both shown here, are often confused. The fruits of the black mulberry are a real delicacy, while the leaves of the white mulberry are the staple diet of the silk worm. Photo by The Board of Trustees of the Royal Botanic Gardens, Kew

The black mulberry is a long-lived, stately tree. With age, the gnarled trunk often leans at an angle and has to be propped up to provide support. The spreading branches with heart-shaped leaves sometimes droop to the ground and bear the succulent dark purple, almost black, raspberry-like fruits with a unique, sub-acid taste that this tree is often grown for.

These two mulberries are frequently confused in cultivation and sometimes are wrongly planted for their intended use. This is exactly what King James I of England did in the seventeenth century when he wanted to compete with the silk industries of Italy and France. Thousands of mulberry trees were imported and the king had his own 1.6-hectare (4-acre) orchard planted in a garden north of present-day Buckingham Palace. The trees were cultivated by what were known as the “King’s Mulberry Men.” In 1609 James wrote to his lord lieutenants to encourage them to plant groves of mulberries as a food source for the silk worm (Bombyx mori) which produce the silk threads for weaving into this delicate cloth. Unfortunately, it was the black mulberry that was planted: although the silk worms will feed on the black mulberry, they much prefer the leaves of the white mulberry (something the French were aware of) and the silk industry failed in Britain.

The white mulberry has been cultivated in China for thousands of years for silk production. Having fed on the leaves of the tree, the silk worm forms a cocoon; these are collected and the fibres are spun and made into silk. The process now takes place in industrial facilities. Photo by Wellcome Collection

It may have been a mistake, but if so it was a fortunate one, as the black mulberry grows better in Britain and had in fact been cultivated there well before King James’s day. The Romans considered the fruits a real delicacy and also used them in medicines. Today they are still highly regarded for conserves and drinks, and are popular with ice cream makers and gin distillers. A word of warning, however — they are impossible to pick without the juice oozing from the ripe fruits, which will permanently stain any garments blood red.

The Roman poet Ovid explained the origin of the fruit’s striking color in the fourth book of his Metamorphoses, which William Shakespeare then incorporated in A Midsummer Night’s Dream. In this tale of forbidden love, Pyramus and Thisbe plan secretly to marry beneath a mulberry tree. Thisbe, arriving first, flees from the meeting place after a lion appears; she drops her scarf, which is torn and bloodied by the beast. Pyramus then discovers the bloodstained scarf, and, supposing his beloved to be dead, he stabs himself and his blood stains the white fruits of the tree a dark red. From that day on, the juice of the fruit remained a deep, ruby red.

More from Remarkable Trees:

Cover courtesy of University of Chicago Press

Reprinted with permission from Remarkable Trees by Christina Harrison and Tony Kirkham published by The University of Chicago Press. © 2019 Thames & Hudson Ltd and the Board of Trustees of the Royal Botanic Gardens, Kew All rights reserved.

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